Apparatus and method to achieve continuous interface and ultrathin film during atomic layer deposition

ABSTRACT

A method and apparatus for performing atomic layer deposition in which a surface of a substrate is pretreated to make the surface of the substrate reactive for performing atomic layer deposition.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/470,279, nowU.S. Pat. No. 6,503,330 filed Dec. 22, 1999, entitled “Apparatus andMethod to Achieve Continuous Interface and Ultrathin Film During AtomicLayer Deposition.”

The United States Government has rights in this invention pursuant toContract No. F33615-99-C-2961 between Genus, Inc. and the U.S. Air ForceResearch Laboratory.

BACKGROUND OF THE INVENTION

The present invention relates generally to semiconductor technology and,more particularly, to a method and apparatus for the practice of atomiclayer deposition.

In the manufacture of integrated circuits, many methods are known fordepositing and forming various layers on a substrate. Chemical vapordeposition (CVD) and its variant processes are utilized to deposit thinfilms of uniform and, often times conformal coatings over high-aspectand uneven features present on a wafer. However, as device geometriesshrink and component densities increase on a wafer, new processes areneeded to deposit ultrathin film layers on a wafer. The standard CVDtechniques have difficulty meeting the uniformity and conformityrequirements for much thinner films.

One variant of CVD to deposit thinner layers is a process known asatomic layer deposition (ALD). ALD has its roots originally in atomiclayer epitaxy, which is described in U.S. Pat. Nos. 4,058,430 and4,413,022 and in an article titled “Atomic Layer Epitaxy” by Goodman etal.; J. Appl. Phys. 60(3), Aug. 1, 1986; pp. R65-R80. Generally, ALD isa process wherein conventional CVD processes are divided intosingle-monolayer depositions, wherein each separate deposition steptheoretically reaches saturation at a single molecular or atomicmonolayer thickness or less and, then, self-terminates.

The deposition is an outcome of chemical reactions between reactivemolecular precursors and the substrate (either the base substrate orlayers formed on the base substrate). The elements comprising the filmare delivered as molecular precursors. The desired net reaction is todeposit a pure film and eliminate “extra” atoms (molecules) thatcomprise the molecular precursors (ligands). In a standard CVD process,the precursors are fed simultaneously into the reactor. In an ALDprocess, the precursors are introduced into the reactor separately,typically by alternating the flow, so that only one precursor at a timeis introduced into the reactor. For example, the first precursor couldbe a metal precursor containing a metal element M, which is bonded to anatomic or molecular ligand L to form a volatile molecule ML_(x). Themetal precursor reacts with the substrate to deposit a monolayer of themetal M with its passivating ligand. The chamber is purged and, then,followed by an introduction of a second precursor. The second precursoris introduced to restore the surface reactivity towards the metalprecursor for depositing the next layer of metal. Thus, ALD allows forsingle layer growth per cycle, so that much tighter thickness controlscan be exercised over standard CVD process. The tighter controls allowfor ultrathin films to be grown.

In practicing CVD, a nucleation step is assumed when a film of stablematerial is deposited on a stable substrate. Nucleation is an outcome ofonly partial bonding between the substrate and the film being deposited.Molecular precursors of CVD processes attach to the surface by a directsurface reaction with a reactive site or by CVD reaction between thereactive ingredients on the surface. Of the two, the CVD reactionbetween the reactive ingredients is more prevalent, since theingredients have much higher affinity for attachment to each other. Onlya small fraction of the initial film growth is due to direct surfacereaction.

An example of nucleation is illustrated in FIGS. 1-3. FIG. 1 shows asubstrate 10 having bonding locations 11 on a surface of the substrate.Assuming that the CVD reaction involves a metal (M) and a ligand (L_(x))reacting with a non-metal (A) and hydrogen (H_(z)), the adsorbed speciesdiffuse on the surface and react upon successful ML_(x)-AH_(z)collisions. However, the reaction does not occur at all of the potentialattachment (or bonding) locations 11. Generally, defect sites (siteshaving irregular topology or impurity) are likely to trap molecularprecursors for extended times and, therefore, have higher probability toinitiate nucleation. In any event, as shown in FIG. 1, the bonding ofthe precursor to the surface occurs at only some of the bondinglocations 12.

Subsequently, as shown in FIG. 2, the initial bonding sites 12 commenceto further grow the thin film material on the surface of the substrate10. The initial reaction products on the surface are the nucleationseed, since the attached products are immobile and diffusing molecularprecursors have a high probability to collide with them and react. Theprocess results in the growing of islands 13 on the substrate surfacetogether with the continuous process of creating new nucleation sites14. However, as the islands 13 grow larger, the formation of newnucleation seeds is suppressed because most of the collisions occur atthe large boundaries of the islands 13.

As the islands 13 enlarge three-dimensionally, most of the adsorptionand reaction processes occur on the island surfaces, especially alongthe upper surface area of the islands 13. Eventually, this verticalgrowth results in the islands becoming grains. When the grains finallycoalesce into a continuous film, the thickness could be on the order of50 angstroms. However, as shown in FIG. 3, the separated nucleationsites can result in the formation of grain boundaries and voids 15 alongthe surface of the substrate, where potential bonding sites failed toeffect a bond with the precursor(s). The grain boundaries and voids 15leave bonding gaps along the surface of the substrate so thatsubstantial film height will need to be reached before a continuousupper surface of the film layer is formed.

Although the results described above from nucleation is a problem withthe standard CVD process, the effect is amplified with ALD. Since ALDutilizes one precursor at a time, the initial bonding will occur due tosurface reaction of the initial precursor with sparse surface defects.Accordingly, seed nucleation sites 12 are very sparse (more sparse thanCVD) and nucleation proceeds by growing ALD layers on these few seedsites. As a result, the nuclei grow three-dimensional islands 13 andcoalesce only at thickness that are comparable to the distance betweenthe nucleation seeds. That is, the voids 15 could be much larger insize, so that a much higher structure is needed to provide a continuosupper surface for the film when only ALD is used.

Accordingly, if an ALD film can initiate growth on a substratepredominantly by nucleation, the film grows discontinuously for a muchthicker distance. Ultimately a much thicker film is practically neededin the case of ALD to achieve continuous film, than that which can beobtained from CVD processes.

The present invention is directed to providing a technique to depositALD thin films of reduced thickness that has continuous interface andfilm.

SUMMARY OF THE INVENTION

A method and apparatus for performing atomic layer deposition in which asurface of a substrate is pretreated to make the surface of thesubstrate reactive for performing atomic layer deposition (ALD). As aresult, the ALD process can start continuously without nucleation orincubation, so that continuous interfaces and ultrathin films areformed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram showing a problem encountered withprior art CVD processes, in which sparse seed nuclei are formed toinitiate film growth by non-continuous nucleation.

FIG. 2 is a cross-sectional diagram showing the start of nucleationemanating from the chemical attachment shown in FIG. 1, in which thespacing between the nucleation sites results in the formation ofseparated islands as the deposition process progresses.

FIG. 3 is a cross-sectional diagram showing the result of further growthof the deposited layer of FIG. 2, in which the formation of grainboundaries and voids requires more than desirable thickness to bedeposited to obtain a continuous layer at the surface.

FIG. 4 is a cross-sectional diagram showing an embodiment of the presentinvention in pretreating a surface of a substrate to activate thesurface, prior to performing atomic layer deposition to grow an ultrathin film layer.

FIG. 5 is a cross-sectional diagram showing the presence of many moreactive sites on the surface of the substrate after surface pretreatmentshown in FIG. 4 is performed.

FIG. 6 is a cross-sectional diagram showing a first sequence forperforming ALD when a first precursor is introduced to the preparedsurface of FIG. 5.

FIG. 7 is a cross-sectional diagram showing a formation of ligands onthe substrate surface of FIG. 6 after the first precursor reacts withthe pretreated surface and the subsequent introduction of a secondprecursor.

FIG. 8 is a cross-sectional diagram showing the restoration of thesubstrate surface of FIG. 7 so that the first precursor can bereintroduced to repeat the ALD cycle for film growth and, in addition, acontinuous interface layer of the desired film is deposited on thesubstrate by the sequences of FIGS. 5-7.

FIG. 9 is a cross-sectional diagram showing a formation of a next ALDmonolayer atop the first monolayer shown in FIG. 8 to further grow thelayer above the substrate one atomic/molecular layer at a time.

FIG. 10 is a cross-sectional diagram showing an alternative pretreatmenttechnique in which an intermediate layer is formed to provide activationsites on the surface of the substrate prior to performing ALD.

FIG. 11 is a block diagram showing one reactor apparatus for performingALD, as well as pretreating the surface by practicing the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The practice of atomic layer deposition (ALD) to deposit a film layeronto a substrate, such as a semiconductor wafer, requires separatelyintroducing molecular precursors into a processing reactor. The ALDtechnique will deposit an ultrathin film layer atop the substrate. Theterm substrate is used herein to indicate either a base substrate or amaterial layer formed on a base substrate, such as a silicon substrate.The growth of the ALD layer follows the chemistries associated withchemical vapor deposition (CVD), but the precursors are introducedseparately.

In an example ALD process for practicing the present invention, thefirst precursor introduced is a metal precursor comprising a metalelement M bonded to atomic or molecular ligand L to make a volatilemolecule ML_(x) (the x, y and z subscripts are utilized herein to denoteintegers 1, 2, 3, etc.). It is desirable that the ML_(x) molecule bondwith a ligand attached to the surface of the substrate. An exampleligand is a hydrogen-containing ligand, such as AH, where A is anonmetal element bonded to hydrogen. Thus, the desired reaction is notedas

AH+ML_(x)→AML_(y)+HL,

where HL is the exchange reaction by-product.

However, in a typical situation as noted in the Background sectionabove, the substrate surface does not possess ample bonding sites forall the potential locations on the surface. Accordingly, the ML_(x)precursor bonding to the surface can result in the formation of islandsand grains which are sufficiently far apart to cause the problems notedabove. In order to grow continuous interfaces and films, the presentinvention is practiced to pretreat the surface of the substrate prior toALD in order to have the surface more susceptible to ALD. In thepreferred embodiment the substrate surface is first treated to make thesurface more reactive. This is achieved by forming reactive terminationon the surface which will then react with the first ALD precursor.

FIG. 4 shows one embodiment for practicing the present invention. InFIG. 4, a substrate 20 (again, substrate is used herein to refer toeither a base substrate or a material layer formed on a base substrate)is shown upon which ALD is performed. Instead of applying the ML_(x)precursor initially onto the substrate 20, one or more radicalspecie(s), including such species as oxygen, hydrogen, OH, NH₂, Cl andF, is introduced to react with a surface 21 of the substrate 20. Thespecies can be remote plasma generated and carried to the processingchamber. The reactive species can be selected to react with mostsurfaces, however, the particular specie selected will depend on thesurface chemistry. A given specie is utilized to modify the surface 21.The reactive specie typically will modify the surface by exchangingother surface species and/or attaching to previously reconstructedsites.

For example, SiO₂ surface with approximately 100% siloxane SiOSi bridgeis generally inert. OH, H or O radical exposure can efficiently insertHOH into the SiOSi to generate 2 Si—OH surface species that are highlyreactive with ML_(x) molecular precursor. In FIG. 4, a generic AH_(z)reaction is shown to treat the surface 21 of the substrate 20. A numberof example reactions using a particular species to treat varioussurfaces is described later below.

The introduction of the pretreatment plasma into the processing chambercontaining the substrate 20 results in the formation of surface speciesat various desired bonding sites. Thus, as shown in FIG. 5, the surfaceis shown containing AH sites. It is desirable to have the AH species atmany of the potential bonding sites. Subsequently, as shown in FIG. 6,the first precursor ML_(x) is introduced to start the ALD process forgrowing a film layer having the composition MA.

It should be noted that the prior art practice of performing ALDcommences by the introduction of ML_(x). Since the prior art does notpretreat the surface 21, there is a tendency for the surface to have lotless potential bonding sites. That is, there are lot less AH sites onnon-treated surfaces versus the number available for the pretreatedsurface 21 shown in FIG. 6. Accordingly, with less bonding sites on thesurface, the earlier described problems associated with nucleation canoccur. However, the pretreated surface 21 allows for many more bondingsites to be present on the surface to reduce the above-noted problem.

FIGS. 7-9 show the remaining sequence for performing ALD. After theML_(x) precursor is introduced, the

AH+ML_(x)→AML_(y)+HL

reaction occurs, wherein HL is exchanged as the reaction by-product. Asshown in FIG. 7, the surface of the substrate 21 now contains the MA-Lcombination, which then reacts with the second precursor comprisingAH_(z). The second precursor, shown here comprising a nonmetal element Aand hydrogen reacts with the L terminated sites on the surface 21. Thehydrogen component is typically represented by H₂O, NH₃ or H₂S. Thereaction

ML+AH_(z)→MAH+HL

results in the desired additional element A being deposited as AHterminated sites and the ligand L is eliminated as a volatile by-productHL. The surface 21 now has AH terminated sites, as shown in FIG. 8.

At this point of the process, the first precursor has been introducedand deposited by ALD, followed by the second precursor, also by ALD. Thesequence of surface reactions restores the surface 21 to the initialcondition prior to the ML_(x) deposition, thereby completing the ALDdeposition cycle. Since each ALD deposition step is self-saturating,each reaction only proceeds until the surface sites are consumed.Therefore, ALD allows films to be layered down in equal meteredsequences that are identical in chemical kinematics, deposition percycle, composition and thickness. Self-saturating surface reactions makeALD insensitive to transport non-uniformity either from flow engineeringor surface topography, which is not the case with other CVD techniques.With the other CVD techniques, non-uniform flux can result in differentcompletion time at different areas, resulting in non-uniformity ornon-conformity. ALD, due to its monolayer limiting reaction, can provideimproved uniformity and/or conformity over other CVD techniques.

FIG. 9 illustrates the result of a subsequent ALD formation of the MAlayer when the next ML_(x) sequence is performed to the surface of thesubstrate shown in FIG. 8. Thus, additional ALD deposition cycles willfurther grow the film layer 22 on the surface 21, one atomic ormolecular layer at a time, until a desired thickness is reached. Withthe pretreatment of the surface 21, nucleation problems noted earlierare inhibited, due to ample bonding sites on the surface. Thus, theinitial ALD layers, as well as subsequent ALD layers, will have amplebonding sites on the surface to attach the reactive species. Continuousultrathin film layers of 50 angstroms and under can be deposited withacceptable uniformity and conformity properties when practicing thepresent invention.

It is appreciated that the pretreatment of the surface 21 can beachieved to deposit enough radical species to exchange with the surface.In this instance, these radical species (shown as AH in the exampleillustrated) provide termination sites for bonding to the ML_(x)precursor. However, in some instances, it may be desirable to actuallydeposit an intermediate layer above the surface 21. In this instance, anactual intermediate layer 23 is formed above the surface 21 and in whichthe termination sites are actually present on this layer 23. This isillustrated in FIG. 10. Again, this layer can be deposited by a plasmaprocess, including ALD. Then, the ALD process sequence, commencing withthe deposition of ML_(x) can commence.

An intermediate layer may be required in some instances when thesubstrate cannot be made reactive with either of the ALD molecularprecursors by a simple attachment or exchange of surface species. Theultra thin intermediate layer 23 is deposited as part of thepretreatment process. The intermediate layer 23 provides a new surfacethat is reactive to one or both precursors. The layer 23 is formedhaving a thickness which is kept minimal, but sufficient for activation.The intermediate layer 23 may be conductive, semiconductive orinsulating (dielectric). Typically, it will match the electricalproperties of either the substrate 20 or the overlying film being grown.For example, layer 23 is needed as a transition layer when W or WN_(x)films are deposited on SiO₂. In this instance, Al₂O₃ (which is aninsulator) or TiN, Ti, Ta or Ta_(x)N (which are conductors) can be usedfor the intermediate layer 23.

It is to be noted further, that the intermediate layer 23 can bedeposited by ALD for the pretreatment of the surface. Additionally, thesurface 21 of the substrate 20 can be pretreated first by the firstmethod described above to prepare the surface 21 for the deposition ofthe intermediate layer 23. Although this does require additionalprocess, it may be desirable in some instances.

It is appreciated that the pretreatment of surface 21 is achieved by aplasma process in the above description, including the use of ALD.However, other techniques can be used instead of a plasma process topretreat the surface 21. Thus, the surface 21 can be treated, even theintermediate layer 23 grown, by other techniques. Furthermore, aleaching process can be utilized. Since some surfaces are quite inert, aprocess other than reactive exchange or attachment may be desirable. Forexample, hydrocarbon and fluorocarbon polymers are utilized for low-kdielectrics. Adhesion of films, for sealing (insulating) or for forminga barrier (metals, metal nitrides), is difficult to achieve. In theseinstances, leaching hydrogen or fluorine from the top layer of thepolymer can activate the surface for ALD.

Thus, a number of techniques are available for pretreating a surface ofa substrate so that the surface is more active for ALD. The presentinvention can be implemented in practice by a number of chemistries andchemical reactions. A number of examples are provided below withrelevant equations. It is to be understood that the examples listedbelow are provided as examples and in no way limit the invention to justthese examples.

EXAMPLE 1

ALD deposition of Al₂O₃ on Silicon A silicon substrate is firstactivated (pretreated) by forming thin layers of silicon oxide (SiO₂) orsilicon oxinitride, in which OH and/or NH_(x) groups form theterminations. The process involves O₂/H₂/H₂O/NH₃ remote plasma thatincludes different ratios of the constituents to form the terminationsprior to the introduction of the first precursor to grow the Al₂O₃ thinfilm layer on silicon.

Si—H+OH.+H.+NH_(x).→Si—OH+Si—NH_(x) (where “.” defines a radical)

 Si—OH+Al(CH₃)₃→Si—O—Al(CH₃)₂+CH₄

Si—NH_(x)+Al(CH₃)₃→Si—NH_(x-1)—Al(CH₃)₂+CH₄

EXAMPLE 2

ALD deposition of Al₂O₃ on Silicon. The silicon substrate is activatedby forming thin layers of SiO₂ that is hydroxilated by exposing HFcleaned (H terminated) silicon to a pulse of H₂O at temperatures below430° C. This process results in a self-saturated layer of SiO₂ that isapproximately 5 angstroms thick.

Si—H+H₂O→Si—O—Si—OH+H₂

Si—OH+Al(CH₃)₃→Si—O—Al(CH₃)₂+CH₄

EXAMPLE 3

ALD deposition of Al₂O₃ on WN_(x). NH₃/H₂/N₂ plasma is used to leachfluorine from the top layers of the WN_(x) film and terminate thesurface with NH_(x) species. These species are reacted with trimethylaluminum (TMA) to initiate deposition of Al₂O₃ on WN_(x).

W_(x)N+H.+NH_(x).→W—NH_(x)

W—NH_(x)+Al(CH₃)₃→W—NH_(x-1)—Al(CH₃)₂+CH₄

EXAMPLE 4

ALD deposition of Al₂O₃ on TiN. NH₃/H₂/N₂ plasma is used to terminatethe surface with NH_(x) species. These species are reacted with TMA toinitiate Al₂O₃ ALD.

TiN+H.+NH_(x).→Ti—NH_(x)

TiNH_(x)+Al(CH₃)₃→TiNH_(x-1)—Al(CH₃)₂+CH₄

EXAMPLE 5

ALD deposition of Al₂O₃ on Ti. NH₃/H₂/N₂ plasma is used to nitridize thesurface and terminate the surface with NH_(x) species. Maintainconditions to avoid extensive nitridization into the Ti film. The NH_(x)species are reacted with TMA to initiate Al₂O₃ ALD.

Ti+NH_(x).+H.→TiNH_(x)

 TiNH_(x)+Al(CH₃)₃→TiNH_(x-1)—Al(CH₃)₂+CH₄

EXAMPLE 6

ALD deposition of Al₂O₃ on W. NH₃/H₂/N₂ plasma is used to nitridize thesurface and terminate the surface with NH_(x) species. Maintainconditions to avoid extensive nitridization into the W film. The NH_(x)species are reacted with TMA to initiate Al₂O₃ ALD.

W+NH_(x).+H.→WNH_(x)

W—NH_(x)+Al(CH₃)₃→W—NH_(x-1)—Al(CH₃)₂+CH₄

EXAMPLE 7

ALD deposition of Al₂O₃ on Ta. NH₃/H₂/N₂ plasma is used to nitridize thesurface and terminate the surface with NH_(x) species. Maintainconditions to avoid extensive nitridization into the Ta film. The NH_(x)species are reacted with TMA to initiate Al₂O₃ ALD.

Ta+NH_(x).+H.→TaNH_(x)

TaNH_(x)+Al(CH₃)₃→TaNH_(x-1)—Al(CH₃)₂+CH₄

EXAMPLE 8

ALD deposition of Al₂O₃ on Ta_(x)N. NH₃/H₂/N₂ plasma is used toterminate the surface with NH_(x) species. The NH_(x) species arereacted with TMA to initiate Al₂O₃ ALD.

Ta_(x)N+NH_(x).+H.→TaNH_(x)

TaNH_(x)+Al(CH₃)₃→TaNH_(x-1)—Al(CH₃)₂ 30 CH₄

EXAMPLE 9

ALD deposition of Ta₂O₅ on Al₂O₃. The process involves O₂/H₂/H₂O remoteplasma that includes different ratios of the constituents. This plasmais used to terminate the surface with OH species that are reactive withTaCl₅.

Al₂O₃+OH.+O.+H.→Al₂O₃—OH

Al₂O₃—OH+TaCl₅→Al₂O₃—O—TaCl₄+HCl

EQUATION 10

ALD deposition of Al₂O₃ on Ta₂O₅. The process involves O₂/H₂/H₂O remoteplasma that includes different ratios of the constituents. This plasmais used to terminate the surface with OH species that are reactive withTaCl₅.

Ta₂O₅+O.+H.+OH.→Ta₂O₅—OH

Ta₂O₅—OH+Al(CH₃)₃→Ta₂O₅—O—Al(CH₃)₂+CH₄

EXAMPLE 11

ALD deposition of TiO_(x) on Al₂O₃. The process involves O₂/H₂/H₂Oremote plasma that includes different ratios of the constituents. Thisplasma is used to terminate the surface with OH species that arereactive with TMA.

Al₂O₃+O.+H.+OH.→Al₂O₃—OH

Al₂O₃—OH+TiCl₄→Al₂O₃—O—TiCl₃+HCl

EXAMPLE 12

ALD deposition of Al₂O₃ on TiO_(x). The process involves O₂/H₂/H₂Oremote plasma that includes different ratios of the constituents. Thisplasma is used to terminate the surface with OH species that arereactive with TiCl₄.

TiO₂+O.+H.+OH.→TiO₂—OH

TiO₂—OH+Al(CH₃)₃→TiO₂—O—Al(CH₃)₂+CH₄

EXAMPLE 13

ALD deposition of TiO_(x) on TiN. NH₃/H₂/N₂ plasma is used to terminatethe surface with NH_(x) species. The NH_(x) species are reacted withTiCl₄ to initiate TiO_(x) ALD.

TiN+H.+NH_(x).→Ti—NH_(x)

Ti—NH_(x)+TiCl₄→TiNH_(x-1)—TiCl₃+HCl

EXAMPLE 14

ALD deposition of W on TiN. NH₃/H₂/N₂ plasma is used to terminate thesurface with NH_(x) species. The NH_(x) species are reacted with TiCl₄to initiate TiN ALD.

TiN+H.+NH_(x).→Ti—NH_(x)

 Ti—NH_(x)+WF₆→TiNH_(x-1)—WF₅+HF

EXAMPLE 15

ALD deposition of WN_(x) on TiN. NH₃/H₂/N₂ plasma is used to terminatethe surface with NH_(x) species. The NH_(x) species are reacted withTiCl₄ to initiate WN_(x) ALD.

TiN+H.+NH_(x).→Ti—NH_(x)

Ti—NH_(x)+WF₆→TiNH_(x-1)—WF₅+HF

EXAMPLE 16

ALD deposition of WN_(x) on SiO₂. O₂/H₂/H₂O remote plasma that includesdifferent ratios of the constituents is used to terminate the surfacewith OH species that are reactive with TiCl₄. The TiCl₄ species is usedto grow an intermediate layer of Ti or TiN. The final layer isterminated with NH_(x) species (from the TiN ALD) which reacts with WF₆to initiate the WN_(x) ALD process.

SiO₂+H.+O.+OH.→Si—OH

Si—OH+TiCl₄→SiO—TiCl₃+HCl

SiO—TiCl₃+NH₃→SiO—TiN—NH_(x)+HCl

SiO—TiN—NH_(x)+WF₆→SiO—TiN—NH_(x-1)WF₅+HF

EXAMPLE 17

ALD deposition of W on SiO₂. O₂/H₂/H₂O remote plasma that includesdifferent ratios of the constituents is used to terminate the surfacewith OH species that are reactive with TiCl₄. The TiCl₄ species is usedto grow an intermediate layer of Ti or TiN. The final layer isterminated with NH_(x) species (from the TiN ALD) which reacts with WF₆to initiate the W ALD process.

SiO₂+H.+O.+OH.→Si—OH

Si—OH+TiCl₄→SiO—TiCl₃+HCl

SiO—TiCl₃+NH₃→SiO—TiN—NH_(x)+HCl

SiO—TiN—NH_(x)+WF₆→SiO—TiN—NH_(x-1)WF₅+HF

Alternatively, TaCl₅ can be used for growing an intermediate Ta_(x)Nlayer.

EXAMPLE 18

ALD deposition of WN_(x) on hydrocarbon polymer (Low-k DielectricLayer). NF₃ remote plasma generates fluorine atoms that leach outhydrogen from the hydrocarbon. The leached surface is reacted with TiCl₄and followed by TiN or Ti/TiN ALD of a thin intermediate layer. TheNH_(x) terminated surface that is prepared during the TiN ALD is reactedwith WF₆ to initiate WN_(x) ALD.

C_(n)H_(m)+F.→C_(p)H_(q)C.

C_(p)H_(q)C.+TiCl₄→C_(p)H_(q-1)CTiCl₃+HCl

C_(p)H_(q-1)CTiCl₃+NH₃→C_(p)H_(q-1)CTiN—NH_(x)+HCl

C_(p)H_(q-1)CTiN—NH_(x)+WF₆→C_(p)H_(q-1)CTiN_(x-1)—WF₅+HF

EXAMPLE 19

ALD deposition of WN_(x) on perfluorocarbon polymer (Low-k DielectricLayer). H₂/NH₃ remote plasma generates H atoms and NH_(x) radicals thatleach out fluorine from the hydrocarbon. The leached surface is reactedwith TiCl₄ and followed by TiN or Ti/TiN ALD of a thin intermediatelayer. The NH_(x) terminated surface that is prepared during the TiN ALDis reacted with WF₆ to initiate WN_(x) ALD.

C_(m)F_(n)+H.+NH_(x).→C_(p)F_(q)C.+HF

C_(p)F_(q)C.+TiCl₄→C_(p)F_(q)C—TiN—NH_(x)

C_(p)F_(q)C—TiN—NH_(x)+WF₆→C_(p)F_(q)C—TiNH_(x-1)—NWF₅+HF

EXAMPLE 20

ALD deposition of oxide on another oxide. The surface of the first oxideis activated by O₂/H₂/H₂O remote plasma that includes different ratiosof the constituents. This process is used to terminate the surface withOH species that are reactive with a metal precursor for the next oxidelayer.

M1O_(x)+O.+H.+OH.→M1O_(x)—OH

M1O_(x)—OH+M2L_(y)→M1O_(x)—O—M2L_(y-1)+HL

EXAMPLE 21

ALD deposition of oxide on metal, semiconductor or metal nitride.NH₃/H₂/N₂ plasma is used to terminate the surface with NH_(x) speciesthat are reactive with a metal precursor for initiating ALD.

M1+H.+NH_(x).→M1—NH_(x)

M1NH_(x)+M2L_(y)→M1NH_(x-1)M2L_(y-1)+HL

EXAMPLE 22

ALD deposition of metal, semiconductor or conductive metalnitride onoxide. NH₃/H₂/N₂ plasma is used to terminate the surface with NH_(x)species or O₂/H₂/H₂O plasma generated radicals are used to terminate thesurface with OH species. The species are reactive with a metal precursorfor initiating ALD.

M1O_(x)+O.+H.+OH.→M1O_(x)—OH

M1O_(x)—OH+M2L_(y)→M1O_(x)—O—M2L_(y-1)+HL

Again, it is appreciated that the above are described as examples onlyand that many other ALD reactions and pretreatment procedures areavailable.

Referring to FIG. 11, an apparatus for practicing the present inventionis shown. An ALD reactor apparatus 30 is shown as one embodiment. It isappreciated that a variety of other devices and equipment can beutilized to practice the invention. Reactor 30 includes a processingchamber 31 for housing a wafer 32. The wafer 32 comprises the substrate20 described in the earlier Figures. Typically, the wafer 32 residesatop a support (or chuck) 33. A heater 34 is also coupled to the chuckto heat the chuck 33 and the wafer 32 for plasma deposition. Theprocessing gases are introduced into the chamber 31 through a gasdistributor 35 located at one end of the chamber 31. A vacuum pump 36and a throttling valve 37 are located at the opposite end to draw andregulate the gas flow across the wafer surface.

A mixing manifold 38 is used to mix the various processing gases and themixed gases are directed to a plasma forming zone 39 for forming theplasma. A variety of CVD techniques for combining gases and formingplasma can be utilized, including adapting techniques known in the art.The remotely formed plasma is then fed into gas distributor 35 and theninto the chamber 31.

The mixing manifold 38 has two inlets for the introduction of gases andchemicals. A carrier gas is introduced and the flow split at the mixingmanifold 38. The carrier gas is typically an inert gas, such asnitrogen. The mixing manifold 38 also has two inlets for the chemicals.In the example diagram of FIG. 11, chemical A and chemical B are showncombined with the carrier gas. Chemistry A pertains to the firstprecursor and chemistry B pertains to the second precursor forperforming ALD for the two precursor process described above. Chemicalselection manifold 40 and 41, comprised of a number of regulated valves,provide for the selecting of chemicals that can be used as precursors Aand B, respectively. Inlet valves 42 and 43 respectively regulate theintroduction of the precursor chemistries A and B into the mixingmanifold 38.

The operation of the reactor for performing ALD is as follows. Once thewafer is resident within the processing chamber 31, the chamberenvironment is brought up to meet desired parameters. For example,raising the temperature of the wafer in order to perform ALD. The flowof carrier gas is turned on so that there is a constant regulated flowof the carrier gas as the gas is drawn by the vacuum created by the pump36. When ALD is to be performed, valve 42 is opened to allow the firstprecursor to be introduced into the carrier gas flow. After apreselected time, valve 42 is closed and the carrier gas purges anyremaining reactive species. Then, valve 43 is opened to introduce thesecond precursor into the carrier gas flow. Again after anotherpreselected time, the valve 43 is closed and the carrier gas purges thereactive species form the chambers of the reactor. The two chemicals Aand B are alternately introduced into the carrier flow stream to performthe ALD cycle to deposit a film layer.

When the pretreatment of the surface is to be performed by plasma, thepretreating species can be introduced into the mixing manifold througheither or both of the chemical selection routes through selectionmanifold(s) 40, 41 to mix with the carrier gas. Again, the pretreatmentis performed prior to the initial introduction of the first ALDprecursor used to deposit the film. Accordingly, the introduction of thepretreatment chemistry can be achieved from adapting designs of astandard ALD reactor.

Thus, an apparatus and method to achieve continuous interface andultrathin film during atomic layer deposition is described. The presentinvention allows an ALD process to start continuously without nucleationor incubation and allows ultrathin film layers of 50 angstroms or lessin thickness to be deposited having continuous uniformity and/orconformity.

We claim:
 1. A method to perform atomic layer deposition comprising:pretreating a surface of a substrate or a material layer formed on thesubstrate by introducing a radical specie including any combination ofO₂, H₂, H₂O, NH₃, NF₃, N₂, Cl and F to increase AHx termination sites onthe surface, where x is an integer and A is a non-metal capable ofbonding with hydrogen H; introducing a first precursor to deposit afirst reactive specie on the surface, the surface when pretreated beingmore receptive to have additional bonding with the first reactivespecie, due to the increase of AHx termination sites on the surface; andintroducing a second precursor, after the bonding of the first reactivespecie, to deposit a second reactive specie to react with the depositedfirst reactive specie to form a film layer.
 2. The method of claim 1further including forming the film layer to have a thickness of 50angstroms or less by repeatedly introducing the first precursor followedby the second precursor.
 3. The method of claim 1 wherein saidpretreating the surface includes introducing the radical specie toexchange bonds at the surface of the substrate to increase AHxtermination sites for the first reactive specie.
 4. The method of claim1 wherein said pretreating the surface forms NHx termination sites. 5.The method of claim 1 further comprising forming an intermediate layeron the substrate prior to introducing the first precursor, wherein theradical specie is introduced with the intermediate layer to increasetermination sites for the first reactive specie.
 6. The method of claim1 wherein said pretreating the surface includes introducing the radicalspecie to leach molecules from the substrate to increase terminationsites for the first reactive specie.
 7. The method of claim 1 whereinsaid pretreating further includes introducing the radical specie byplasma.
 8. The method of claim 1 wherein said pretreating furtherincludes introducing the radical specie by plasma and the reactivespecies form the film layer, wherein the film layer is comprised of ametal, metal oxide or metal nitride.
 9. The method of claim 7 whereinAl₂O₃ is deposited on silicon by atomic layer deposition in which saidpretreating includes introducing O₂/H₂/H₂O/NH₃ plasma to form a filmlayer of silicon oxide or silicon oxinitride, in which OH or NH_(x)group forms the termination sites on silicon.
 10. The method of claim 7wherein Al₂O₃ is deposited on WN_(y), where y is an integer, by atomiclayer deposition in which said pretreating includes introducingNH₃/H₂/N₂ plasma to leach fluorine from WN_(y) to form NH_(x) as thetermination sites on WN_(y).
 11. The method of claim 7 wherein Al₂O₃ isdeposited on TiN by atomic layer deposition in which said pretreatingincludes introducing NH₃/H₂/N₂ plasma to form NH_(x) as the terminationsites on TiN.
 12. The method of claim 7 wherein Al₂O₃ is deposited on Tiby atomic layer deposition in which said pretreating includesintroducing NH₃/H₂/N₂ plasma to nitridize the surface to form NH_(x) asthe termination sites on Ti.
 13. The method of claim 7 wherein Al₂O₃ isdeposited on W by atomic layer deposition in which said pretreatingincludes introducing NH₃/H₂/N₂ plasma to nitridize the surface to formNH_(x) as the termination sites on W.
 14. The method of claim 7 whereinAl₂O₃ is deposited on Ta by atomic layer deposition in which saidpretreating includes introducing NH₃/H₂/N₂ plasma to nitridize thesurface to form NH_(x) as the termination sites on Ta.
 15. The method ofclaim 7 wherein Al₂O₃ is deposited on Ta_(y)N, where y is an integer, byatomic layer deposition in which said pretreating includes introducingNH₃/H₂/N₂ plasma to form NH_(x) as the termination sites on Ta_(y)N. 16.The method of claim 7 wherein Ta₂O₅ is deposited on Al₂O₃ by atomiclayer deposition in which said pretreating includes introducingO₂/H₂/H₂O plasma to form OH specie as the termination sites on Al₂O₃.17. The method of claim 7 wherein Al₂O₃ is deposited on Ta₂O₅ by atomiclayer deposition in which said pretreating includes introducingO₂/H₂/H₂O plasma to form OH specie as the termination sites on Ta₂O₅.18. The method of claim 7 wherein TiO_(z), where z is an integer, isdeposited on Al₂O₃ by atomic layer deposition in which said pretreatingincludes introducing O₂/H₂/H₂O plasma to form OH specie as thetermination sites on Al₂O₃.
 19. The method of claim 7 wherein Al₂O₃ isdeposited on TiO_(z), where z is an integer, by atomic layer depositionin which said pretreating includes introducing O₂/H₂/H₂O plasma to formOH specie as the termination sites on TiO_(z).
 20. The method of claim 7wherein TiO_(z), where z is an integer, is deposited on TiN by atomiclayer deposition in which said pretreating includes introducingNH₃/H₂/N₂ plasma to form NH_(x) specie as the termination sites on TiN.21. The method of claim 7 wherein W is deposited on TiN by atomic layerdeposition in which said pretreating includes introducing NH₃/H₂/N₂plasma to form NH_(x) specie as the termination sites on TiN.
 22. Themethod of claim 7 wherein WN_(y), where y is an integer, is deposited onTiN by atomic layer deposition in which said pretreating includesintroducing NH₃/H₂/N₂ plasma to form NH_(x) specie as the terminationsites on TiN.
 23. The method of claim 7 wherein WN_(y), where y is aninteger, is deposited on SiO₂ by atomic layer deposition in which saidpretreating includes introducing O₂/H₂/H₂O plasma to form OH specie thatare reactive with TiCl₄ and in which the TiCl₄ is used to grow anintermediate layer of Ti or TiN to form NH, as the termination sites onTi or TiN.
 24. The method of claim 7 wherein W is deposited on SiO₂ byatomic layer deposition in which said pretreating includes introducingO₂/H₂/H₂O plasma to form OH specie that are reactive with TiCl₄ and inwhich the TiCl₄ is used to grow an intermediate layer of Ti or TiN toform NH_(x) as the termination sites on Ti or TiN.
 25. The method ofclaim 7 wherein W is deposited on SiO₂ by atomic layer deposition inwhich said pretreating includes introducing O₂/H₂/H₂O plasma to form OHspecie that is reactive with TaCl₅ and in which the TaCl₅ is used togrow an intermediate layer of Ta_(z)N, where z is an integer, to formNH_(x) as the termination sites on Ta_(z)N.
 26. The method of claim 7wherein WN_(y), where y is an integer, is deposited on hydrocarbonpolymer by atomic layer deposition in which said pretreating includesintroducing NF₃ plasma to generate fluorine atoms that leach hydrogenfrom the hydrocarbon polymer and in which the leached surface is reactedwith TiCl₄ to grow an intermediate layer of TiN or a combination ofTi/TiN to form NH_(x) as the termination sites on TiN or Ti/TiN.
 27. Themethod of claim 7 wherein WN_(y), where y is an integer, is deposited onperfluorocarbon polymer by atomic layer deposition in which saidpretreating includes introducing H₂/NH₃ plasma to generate hydrogenatoms and NH_(x) radicals that leach fluorine from the hydrocarbonpolymer and in which the leached surface is reacted with TiCl₄ to growan intermediate layer of TiN or a combination of Ti/TiN to form NH_(x)as the termination sites on TiN or Ti/TiN.
 28. The method of claim 7wherein an oxide is deposited on metal, semiconductor or metal nitrideby atomic layer deposition in which said pretreating includesintroducing NH₃/H₂/N₂ plasma to terminate the surface with NH_(x) speciethat are reactive with a metal precursor.
 29. The method of claim 7wherein a metal, semiconductor or conductive metal nitride is depositedas the film layer on oxide by atomic layer deposition in which saidpretreating includes introducing NH₃/H₂/N₂ plasma which is used toterminate the surface with NH_(x) specie.
 30. A method to perform atomiclayer deposition comprising: depositing an intermediate layer;pretreating a surface of the deposited intermediate layer by introducinga radical specie including any combination of O₂, H₂, H₂O, NH₃, NF₃, N₂,Cl and F to increase AHx termination sites on the surface, where x is aninteger and A is a non-metal capable of bonding with hydrogen H;introducing a first precursor to deposit a first reactive specie on thesurface, the surface when pretreated being more receptive to haveadditional bonding with the first reactive specie, due to the increaseof AHx termination sites on the surface; and introducing a secondprecursor, after the bonding of the first reactive specie, to deposit asecond reactive specie to react with the deposited first reactive specieto form a film layer.
 31. A method to perform atomic layer depositioncomprising: leaching hydrogen or fluorine from a surface by pretreatingthe surface by introducing a radical specie including any combination ofO₂, H₂, H₂O, NH₃, NF₃, N₂, Cl and F to increase AHx termination sites onthe surface, where x is an integer and A is a non-metal capable ofbonding with hydrogen H; introducing a first precursor to deposit afirst reactive specie on the surface, the surface when pretreated beingmore receptive to have additional bonding with the first reactivespecie, due to the increase of AHx termination sites on the surface; andintroducing a second precursor, after the bonding of the first reactivespecie, to deposit a second reactive specie to react with the depositedfirst reactive specie to form a film layer.